1. Field of the Invention
The present invention relates to a paper feeding device and an image forming apparatus including the paper feeding device. More particularly, the present invention relates to a paper feeding device of a center feeding type that prevents a sheet of paper from being separated from a finger during installation of the paper feeding device and an image forming apparatus including the paper feeding device.
2. Description of the Related Art
Generally, an image forming apparatus, such as a laser beam printer, an LED (light emitting diode) printer, a digital copier, and a fax machine, produces a monochromatic image or a color image by forming an electrostatic latent image corresponding to a desired image by scanning light onto a photosensitive medium charged to a uniform electrostatic potential. The latent image is then developed by providing developer on the photosensitive medium, and is transferred and fused to a sheet of print paper or an intermediate transfer belt.
The image forming apparatus includes a paper feeding device to feed a sheet of paper. The paper feeding device includes a guide member that guides paper having different widths without paper misalignment.
When a sheet of paper is transferred based on one side of the paper, only the guide member is adjusted to the width of paper and the sheet of paper is transferred (this is referred to as ‘side feeding type’). When a sheet of paper is transferred based on the center of the paper, guide members on both sides of paper are set to the width of the paper and the sheet of paper is transferred while the guide members are facing each other (this is referred to as ‘center feeding type’).
Generally, a paper feeding device of a center feeding type includes a guide member having a pair of guide units to guide both sides of the paper. The guide units are engaged with a pinion gear such that when one of the guide unit and the pinion gear is moved, the other guide unit is moved in association with the movement of the guide unit or the pinion gear. Such a paper feeding device in a printer, copier, or fax machine for office use stores sheets of paper with various sizes, such as A4 sized paper, letter sized paper, and the like.
FIG. 1 is a view of a conventional paper feeding device 10 in which sheets of paper S are stored and pressed by fingers 20. FIG. 2 is a view of the paper feeding device 10 of FIG. 1 that is empty. FIG. 3 is a view of the paper feeding device 10 of FIG. 1 when a sheet of paper S is separated from the fingers 20.
Referring to FIGS. 1-3, the paper feeding device 10 includes a paper feeding cassette 12 and guide units 15. Fingers 20 that are used as paper separation means are installed in the paper feeding cassette 12. The fingers 20 are mounted on both sides of the paper feeding cassette 12 and separate sheets of paper S picked up one by one by a pick-up roller (not shown). A pair of guide units 15 are installed to slide in the direction of the width of a sheet of paper S and to guide both sides of the sheet of paper S stacked in the paper feeding cassette 12.
The conventional paper feeding device 10 has a gap A of a predetermined width between a sidewall of the paper feeding cassette 12 and the guide unit 15, as shown in FIG. 2.
When the paper feeding device 10 is installed in an image forming apparatus after storing sheets of paper therein, a force due to inertia of the sheets of paper is transmitted to a sidewall of the guide unit 15 in an installation direction of the paper feeding device 10. Therefore, the guide unit 15 is pushed in the travel direction of paper S or shaken. Accordingly, the sheet of paper S is undesirably separated from the fingers 20 to the upper side. Since the sheet of paper S is separated from the fingers 20, the fingers 20 cannot function as paper separation means and a paper jam or skew occurs when a sheet of paper is transferred.
In the conventional paper feeding device 10, the guide units 15 cannot be fixed due to the gap A between a sidewall of the paper feeding cassette 12 and each guide unit 15, and therefore a sheet of paper S is separated from the fingers 20 due to the moving of the guide units 15 when the paper feeding device 10 is installed.
Accordingly, a need exists for an image forming apparatus having a paper feeding device that prevents paper from being separated from a finger of the paper feeding cassette during installation of the paper feeding device, thereby substantially preventing paper jams and skews when printing with the image forming apparatus.